1. Field of Invention
The present invention relates to an alloy, more particularly, an Fexe2x80x94Nixe2x80x94Cr alloy used for the electrode of an electron gun. More particularly, the present invention relates to an Fexe2x80x94Crxe2x80x94Ni based alloy exhibiting improved drawing formability and non-magnetism required for such electrode.
2. Description of Related Art
The material which is generally used for the electrode of an electron gun mounted in a color Braun tube and the like is Fexe2x80x94Crxe2x80x94Ni based alloy material. This is non-magnetic stainless steel and is from approximately 0.05 to 0.7 mm of sheet thickness.
The electrongun is a component of the shadow-mask type color Braun tube.
FIG. 1 is a cross-sectional drawing of the shadow-mask type color Braun tube.
FIG. 2 shows an elevational view and a cross-sectional view of the punched part of the electron gun.
Referring to FIG. 1, the fluorescent coating 2, which emits light of the primary colors, i.e., red, green and blue, is applied on the panel 1. The electron beam 3 is emitted from the electron gun 4 provided in the neck portion, and is deflected and scanned by the deflecting yoke 5. The shadow mask is denoted by 6. The magnetic shield is denoted by 7. These parts 1-7 are all known.
In FIG. 2, an example of the formed parts of an electron gun is denoted by 10. The electron beams for light emitting either red, green or blue color pass through the apertures 10a of the part 10. The minute apertures 10 a can be formed by subjecting an Fexe2x80x94Crxe2x80x94Ni based alloy to press-drawing to form a predetermined shape and then punching it to pierce the apertures.
Several techniques for improving the press formability of Fexe2x80x94Crxe2x80x94Ni alloy material are proposed in the following Japanese Patent Applications. It is proposed in Japanese Unexamined Patent Publication (kokai) No. 8-92,691 (Japanese Patent Application No. 6-257253) to facilitate the press drawing, as particularly barring by means of modifying the rolling reduction of area and annealing conditions of the alloy material. The barring works to form an aperture through a strip and to extrude a punch through the aperture so as to widen the aperture. Low-viscosity oil facilitates the detergent operation and hence enhances the press formability. Japanese Unexamined Patent Publication No. 10-30,157 (Japanese Patent Application 8-205,453) relates to such press forming and proposes to measure the central line of surface roughness of the blank material and then to specify the average thickness with respect to the central line and also the maximum roughness so as to further enhance the press formability. According to Japanese Unexamined Patent Publication No. 11-106,873 (Japanese Patent Application No. 9-283,039), an appropriate amount of S is added to ensure the blanking formability and to control trace components to enhance the drawability. This invention is based on a discovery that the burrs left upon press-blanking are related to cracking during the barring.
In recent years, since Braun tubes used for a computer have become more and more miniaturized and luminous, higher level of focusing performance required of the Braun tube. This, in turn, leads to the requirements that the material used for the electron gun has such improved formability as to be capable of forming a large lens diameter with high accuracy and to cope with the increase in the press-forming speed. Under such circumstances, since cracks are formed on the drawn surface 10b (c.f. FIG. 2) of the conventional Fexe2x80x94Crxe2x80x94Ni based alloy material, such material cannot meet fully the requirements mentioned above.
It is an object of the present invention to provide improved alloy material for producing the electrode of an electron gun, which can meet the requirements for drawability, particularly the post-drawing surface quality which has become higher in recent years.
The present inventors discovered that the drawability of Fexe2x80x94Crxe2x80x94Ni based alloy material varies depending upon the degree of preferred orientation of such material, which has been finally annealed, and the distribution of preferred orientation along the direction across the sheet surfaces. More specifically, the drawability is poor when the degree of preferred orientation of the (111) plane is high in the central portion between the sheet surfaces. The draw ability is also poor, when the degree of preferred orientation of the (111) plane is higher on the surfaces of a sheet than in the central portion of the material.
The degree of the preferred orientation of the (111) plane in the central portion between the sheet surfaces of material is expressed by the following formula xcex1c(111)
xcex1c(111)=[Ic(111)/{Ic(111)+Ic(200)+Ic(220)+Ic(311)}]xc3x97100(%)
In this formula, I(hkl) is the integral intensity of diffraction peaks of the (hkl) planes in the central portion between the surfaces of a sheet.
The degree of preferred orientation of the (111) plane on the surface portion of the material is expressed by the following formula xcex1s(111)
xcex1c(111)=[Ic(111)/{Is(111)+Is(200)+Is(220)+Is(311)}]xc3x97100(%)
In this formula, Is(hkl) is the integral intensity of diffraction peaks of the (hkl) planes on the surface portion of a sheet.
In the Fexe2x80x94Nixe2x80x94Cr based alloy material used for the electrode of an electron gun, the degree of preferred orientation of the (111) plane is specified based on the above discovery. In accordance with the present invention there is provided the following Fexe2x80x94Nixe2x80x94Cr based alloy strips used for the electrode of an electron gun.
(1) An Fexe2x80x94Nixe2x80x94Cr based alloy strip having sheet surfaces, essentially consisting of from 15 of 20% of Cr, from 9 to 15% of Ni, the balance being Fe and unavoidable impurities, such percentages being -based on weight, having 0.03% or less of cleanliness as stipulated under JIS G 0555, having final annealed temper and a preferred orientation texture in terms of 50% or less of degree of preferred orientation of the (111) plane in the central portion between the sheet surfaces which is expressed by the following formula:
xcex1c(111)=[Ic(111)/{Ic(200)+Ic(200)+Ic(220)+I(311)}]xc3x97100(%)
In this formula, Ic(hkl) is the integral intensity of diffraction peaks of the (hkl) planes in the central portion between the surfaces of a sheet.
(2) An Fexe2x80x94Nixe2x80x94Cr based alloy strip having sheet surfaces, essentially consisting of from 15 to 20% of Cr, from 9 to 15% of Ni, the balance being Fe and unavoidable impurities, such percentages being based on weight, having 0.03% or less of cleanliness stipulated under JIS G 0555, having final annealed temper and a preferred orientation texture in terms of 50% or less of the xcex1c(111), which is equal to or greater than xcex1s(111) which indicates the degree of preferred orientation of the (111) plane on the surface portion of the material, i.e., xcex1s(111)xe2x89xa6xcex1c(111).
In accordance with the present invention, there is also provided the electrode of an electron gun, consisting of the Fexe2x80x94Crxe2x80x94Ni alloys (1) or (2), mentioned above.